JPH11153556A - Thin-film measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently measure and evaluate the thermal expansion coefficient or Young's modulus of a thin film with fewer man-hours by an inexpensive device. SOLUTION: A thin film to be measured is formed on the upper or lower surface of a plurality of substrates with different thermal expansion coefficients and at the same time known Young's modulus and Poisson ratio while being sufficiently thinner than the substrate, and a plurality of samples 16 to be measured are prepared. The sample 16 is accommodated in a sample rest 12 and at the same time is covered with oil 18. Then, when the sample 16 is heated by a heater 14, shape change is measured by a feeler 22 of a surface displacement meter. Temperature is measured by a thermocouple 20. The measurement results are supplied to a computer 24 for calculating and evaluating the thermal expansion coefficient or Young's modulus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film measuring apparatus for measuring a thermal characteristic such as a coefficient of thermal expansion of a thin film material and an elastic characteristic such as a Young's modulus.

[0002]

2. Description of the Related Art In recent years, miniaturization of electronic devices has been rapidly promoted, and manufacturing techniques thereof have been dramatically improved. As the most effective means for miniaturizing elements, sputtering, vacuum deposition, CVD (Chem
The use of thinning techniques such as ical vapor deposition (chemical vapor deposition) has increased, and with the development of these techniques, the necessity for thin film evaluation techniques has increased.

[0003] As a recent trend, in fields such as thin-film magnetic heads and micromachines, thick films of several tens of µm have begun to be used. In such a case, stress easily accumulates at the interface between the laminated thick film and the substrate or between the film and the film. Further, during the process of manufacturing these thin-film devices, a heat treatment process is included as a matter of course.
Due to the difference between the heat applied at this time and the coefficients of thermal expansion of the substrate and the respective laminated films, the stress state inside the element is excessively changed. These often cause film peeling and deterioration of element characteristics when manufacturing a thin film device.

On the other hand, the coefficient of thermal expansion of a thin film may vary greatly depending on the film forming method and film forming conditions as compared with a bulk material of the same material. Further, the state of the film changes every moment due to the heat history after the film formation, and it is difficult to simply infer from the thermal behavior of the bulk material.

In order to predict the thermal behavior of the film at the time of heating, it is essential to know the coefficient of thermal expansion of the film. Further, in order to know the stress state in the element, it is convenient to grasp elastic properties such as Young's modulus of the film. Further, it is more convenient if the measurement can be performed efficiently with a small number of man-hours. It is preferable that the measuring device is easy to operate and inexpensive to manufacture.

The present invention focuses on the above points,
The purpose is to satisfactorily measure the thermal properties such as the coefficient of thermal expansion of the thin film and the elastic properties such as the Young's modulus. Another object is to easily measure the coefficient of thermal expansion and the Young's modulus.

[0007]

In order to achieve the above object, the present invention provides a method of forming a thin film to be measured on a plurality of substrates having different coefficients of thermal expansion and having known Young's modulus and Poisson's ratio. Heating means for heating the sample; temperature measuring means for measuring the temperature of the sample; displacement measuring means for measuring a change in the shape of the sample during heating by the heating means; measurement results obtained by the temperature measuring means and the displacement measuring means. Calculating means for calculating a thermal characteristic or an elastic characteristic of the thin film to be measured based on the calculated characteristic.

[0008] According to one of the main aspects, the whole of the sample is surrounded by a liquid. According to another embodiment, the displacement measuring means comprises a stylus type surface displacement meter. According to still another aspect, the calculating means performs the calculation based on a rate of a stress change accompanying a temperature change.

The above and other objects, features and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail. FIG. 1 shows a configuration of a measuring apparatus according to the present embodiment. In the same figure, length 20mm x width 3
A copper sample stage 12 provided with a groove 10 of 0 mm x 4 mm depth,
It is fixed to the upper part of the resistance heater 14. A sample 16 smaller than the groove size is placed inside the groove 10, and the entire sample 16 is immersed in silicone oil 18. A thermocouple 20 is embedded on the side of the sample table 12. In addition, a stylus type surface displacement meter 22 is provided above the sample table 12. Thermocouple 20 and surface displacement meter 2
The output side of 2 is connected to a computer 24.

The immersion of the entire sample 16 in silicone oil is as follows.
This is for eliminating the temperature difference between the upper part and the lower part of the sample 16.
Thereby, the deformation of the substrate itself due to the temperature difference between the upper and lower portions of the sample can be eliminated. The thermocouple 20 embedded from the side of the sample stage 12 is for measuring the sample temperature. The deformation of the sample 16 is measured by a stylus 22 of a stylus type surface deformation meter (not shown). The measurement result is input to the computer 24, where the calculation of the thermal expansion coefficient and the like is performed according to the following mathematical formula.

For example, the temperature of the sample 16 is changed from room temperature to 150
Change to ° C. Then, at a certain temperature interval, for example, 20
The shape change of the sample 16 is measured at intervals of ° C. Specifically, when the sample temperature is 20 ° C., the stylus of the stylus type surface deformation meter is moved from left to right of the sample, and the shape change of the sample 16 is measured. Next, the sample stage 12 is heated by the heater 14 to a sample temperature of 40 degrees, and when the sample temperature is 40 degrees, the shape change of the sample 16 is measured as described above. Such a measurement process is repeatedly performed every 20 ° C. until the sample temperature reaches 150 ° C. Next, the measurement process described above is repeated while changing the measurement sample object.

FIG. 2 shows an example in which a change in the warpage of the sample 16 with respect to the heating temperature is measured using this measuring apparatus.
In this example, two types of substrates having different thermal expansion coefficients α are used. (1) Glass substrate; diameter φ = 15 mm, thickness t = 0.65 mm, coefficient of thermal expansion α = 120 × 10 ⁻⁷ / ° C., Young's modulus E = 5.59 × 10 ¹¹ dyn / cm ² , Poisson's ratio = 0 .29

(2) Quartz substrate; diameter φ = 15 mm, thickness t = 0.5 mm, coefficient of thermal expansion α = 5 × 10 ⁻⁷ / ° C., Young's modulus E = 7.27 × 10 ¹¹ dyn / cm ² , Poisson Ratio = 0.17

On these two types of substrates, a 8.7 μm-thick composite oxide film whose thermal expansion coefficient is to be measured is simultaneously formed in the same lot to produce two samples. These two samples 16 were heated by the measuring device, and the shape change due to the temperature change was measured. FIG. 2 shows the measurement results. Graph G1 is for a glass substrate, and graph G2 is for a quartz substrate.

Next, a method for evaluating the thermal expansion coefficient and the elastic modulus of the thin film formed on the sample will be described. The thermal stress σ when a film is present on the substrate is expressed by the following equation (1). σ = E (αf−αs) △ T (1) E = Ef / (1−νf) (2) where Ef: Young's modulus of the film, νf: Film , Αf: thermal expansion coefficient of the film, αs: thermal expansion coefficient of the substrate, ΔT: temperature change. For convenience, equation (2) is treated as the Young's modulus of the film.

Next, a change Δσ in stress due to a temperature change is:
By measuring the change in the amount of warpage of the sample 16, it is derived from the following equation (3). Δσ = (4/3) Es · △ δ · D 2 / {(1-νs) · d · l 2} ............ (3) where, Es: substrate Young's modulus of,? S: Poisson's ratio of the substrate , D: substrate thickness, d: film thickness, l: measured length, δ: warpage (displacement at the midpoint of measured length l).

Therefore, the thermal expansion coefficients αf and E (corresponding to the Young's modulus) of the film can be obtained by measuring the change in the amount of warpage with respect to temperature using two types of substrates having different thermal expansion coefficients αs. That is, the coefficient of thermal expansion of the substrate is α
Assuming that s1, αs2 and stress changes in each substrate are Δσ1, Δσ2, from the above equation (1), Δσ1 / ΔT = E (αf−αs1) = C1 Δσ2 / ΔT = E (αf−αs2) = C2 ... (4) Therefore, αf = (C2 · αs1−C1 · αs2) / (C2−C1) E = (C2−C1) / (αs1−αs2) (5), and it is possible to obtain αf and E of the film. it can. This is important data for understanding the process of stress relaxation by heat treatment.

The inclination of the straight line of the measurement result shown in FIG.
From equation (3), the change Δσ / ΔT of the warp due to the temperature change is obtained for each of the two samples. Furthermore, these two
From the two values, the thermal expansion coefficient α
f and Young's modulus E are obtained. In the measurement example of FIG. 2, αf = 33 × 10 ⁻⁷ / ° C. and E = 16.4 × 10 ¹¹ / cm ² .

As described above, according to the present embodiment, the following effects can be obtained. (1) As shown in FIG. 1, the measuring device has a simple configuration, is easy to manufacture, and is very inexpensive. (2) By the calculation using the measurement result as shown in FIG. 2, the coefficient of thermal expansion and the Young's modulus of the thin film can be efficiently measured with a small number of man-hours.

Next, another measurement example will be described with reference to FIG. As two types of substrates with different coefficients of thermal expansion,
The above-described glass substrate and quartz substrate were used. On these two types of substrates, a film thickness of 5.02 whose thermal expansion coefficient is to be measured is set.
A μm SiO ₂ film is simultaneously formed in the same lot to produce two samples. These samples were heated before and after by the measuring device, and the shape change due to the temperature change was measured. FIG. 3 shows the measurement results. Graph G3 is for a glass substrate, and graph G4 is for a quartz substrate.

Similarly, from the slope of the graph of FIG. 3, the change Δσ / ΔT of the warp due to the temperature change is obtained for each sample.
From these two values, the coefficient of thermal expansion and Young's modulus of the film were determined. In the example of FIG. 3, αf = 5 × 10 ⁻⁷ / ° C. and E = 7.27 × 10 ¹¹ / cm ² .

Next, still another measurement example will be described with reference to FIG. As the two types of substrates having different coefficients of thermal expansion, the above-mentioned glass substrate and this time a silicon substrate were used. The characteristics of the silicon substrate are as follows. Diameter φ = 15 mm, thickness t = 0.384 mm, coefficient of thermal expansion α = 28 × 10 ⁻⁷ / ° C., Young's modulus E = 10.8 × 10 ¹¹ dyn / cm ² , Poisson's ratio = 0.28

On these two types of substrates, a composite oxide film having a film thickness of 5.42 μm whose thermal expansion coefficient is to be measured is simultaneously formed in the same lot to produce two samples. These samples were heated before and after by the measuring device, and the shape change due to the temperature change was measured. FIG. 4 shows the measurement results. Graph G5 is for a glass substrate, and graph G6 is for a silicon substrate.

Similarly, from the slope of the graph of FIG. 4, the change Δσ / ΔT of the warp due to the temperature change is obtained for each sample.
From these values, the thermal expansion coefficient and Young's modulus of the film were determined.
In this measurement, αf = 21 × 10 ⁻⁷ / ° C. and E = 7.21 × 10 ¹¹ / cm ² .

[0026]

As described above, according to the present invention,
Thermal expansion coefficients are different, and a thin film to be measured is formed on the surface of a plurality of substrates whose Young's modulus and Poisson's ratio are known, and the shape change of the sample when heated is measured to determine the thermal characteristics or thermal characteristics of the thin film. The calculation of the elastic characteristic has the following effects. (1) The measuring device is simple and easy to manufacture, and the manufacturing cost is very low. (2) Characteristics such as the coefficient of thermal expansion and Young's modulus of a thin film can be measured with a small number of man-hours.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a measurement example by the measuring device.

FIG. 3 is a diagram showing an example of measurement by the measuring device.

FIG. 4 is a diagram showing an example of measurement by the measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Groove 12 ... Sample stand 14 ... Heater 16 ... Sample 18 ... Oil 20 ... Thermocouple 22 ... Contact probe (surface displacement meter) 24 ... Computer

Claims (4)

[Claims] 1. A heating means for heating a sample in which thin films to be measured are respectively formed on the surfaces of a plurality of substrates having different thermal expansion coefficients and a known Young's modulus and Poisson's ratio; measuring the temperature of the sample Temperature measuring means; displacement measuring means for measuring a change in shape of the sample at the time of heating by the heating means; thermal characteristics or elasticity of the thin film to be measured based on the measurement results by the temperature measuring means and the displacement measuring means. A thin film measuring device comprising: a calculating means for calculating characteristics. 2. The thin film measuring apparatus according to claim 1, wherein the whole of the sample is surrounded by a liquid. 3. A thin film measuring apparatus according to claim 1, wherein said displacement measuring means is a stylus type surface displacement meter. 4. The thin-film measuring apparatus according to claim 1, wherein the calculating means performs the calculation based on a ratio of a change in stress caused by a change in temperature.